The present invention relates to a method of producing superconductors with greater thicknesses or bulk compared to thin film superconductors and more particularly to textured, large-area bulk superconductors identified as high temperature superconductors. The invention also relates to the superconductor components or products.
Bulk superconductors have increased current carrying capacities and are useful in certain product areas where thin film superconductors lack the required performance. The method employed to produce the bulk superconductors is preferably carried out by producing a biaxially textured sheet of a metal or oxide and using this sheet as a large scale seed in combination with superconductor material in a melt process where the melted superconductor material becomes textured as it solidifies by cooling from the region next to the seed through the thickness or bulk.
U.S. Pat. No. 5,869,431 discloses suitable materials for seeds and for superconductors. In addition to methods disclosed in the ""431 patent, some processes in the past have used several individual seeds (spaced apart) with superconductor materials in an attempt to obtain growth of large area bulk material with appropriate texturing. However, uniformity of texturing and melting of the small seeds have been problems.
In this invention, a biaxially textured sheet of oxide or metal is used as a one-piece seed of a size generally that of the desired superconductor component and placed in contact with superconducting material. The superconducting material is melted and then solidified by cooling with solidification starting from a region adjacent to the seed. By this technique, texturing is extended through the bulk of the superconductor with uniformity.
Two techniques for producing the biaxially textured sheet or oxide may be carried out. With a metal such as nickel, the sheet could be rolled and annealed similar to the treatment described for the nickel wire in U.S. patent application Ser. No. 09/568,890 filed May 11, 2000, the disclosure of which is incorporated by reference. Although the metal sheet may have the desired texturing, it may be necessary to add a buffer layer such as an oxide like those disclosed in the ""431 patent or other oxides such as MgO to preserve the texturing during the subsequent melt stage. Another process is to form a textured surface of a metal oxide such as MgO by using an inclined substrate deposition (ISD). The ISD or inclined substrate deposition method is disclosed in copending U.S. patent application entitled Method for Preparing High Temperature Superconductor, serial no. 09/621,272 filed on even date herewith by Uthamalingam Balachandran and Michael P. Chudzik, the disclosure of which is incorporated herein in its entirety.
Accordingly, it is an object of the present invention to provide a bulk superconductor having a thickness of not less than about 100 microns carried by a polycrystalline textured substrate having misorientation angles at the surface thereof not greater than about 15xc2x0.
Another object of the invention is to provide a bulk superconductor having a thickness of not less than about 100 microns and a surface area of not less than about 50 cm2 carried by a polycrystalline textured layer or sheet having a thickness not less than about 10 microns and misorientation angles at the surface thereof not greater than about 15xc2x0.
Still another object of the invention is to provide a process of manufacturing a bulk superconductor having a thickness not less than about 100 microns, comprising providing a polycrystalline biaxially textured layer or sheet material having a thickness not less than about 10 microns and misorientation angles at the surface thereof not greater than about 15xc2x0, and providing a superconductor precursor powder in contact with the polycrystalline biaxially textured substrate material and melting the precursor powders and thereafter cooling the melted powders to grow superconductor material using substantially the entire polycrystalline textured substrate material as a seed to provide a superconductor having a thickness not less than about 100 microns carried by a polycrystalline biaxially textured substrate material.
A final object of the invention is to provide a superconductor having a thickness not less than 100 microns produced by the inventive methods.
The invention consists of certain novel features and a combination of parts hereinafter fully described, illustrated in the accompanying drawings, and particularly pointed out in the appended claims, it being understood that various changes in the details may be made without departing from the spirit, or sacrificing any of the advantages of the present invention.